The primary goal of this study is to examine the effect of a mentor-based intervention on long-term weight loss in overweight adult women. The primary analysis will focus on the effect of this intervention on long-term weight loss in women receiving a mentor-based intervention, with additional analysis focusing on the effect of this intervention on long-term weight loss in women functioning as mentors in this study. Despite short-term (greater than or equal to 6 months) success in weight loss programs, significant weight regain can occur in adults within the 12 months following the initial intervention period. It has been shown that maintaining long-term contact with an intervention program, maintaining exercise, and maintaining healthful eating behaviors are associated with improvements in long-term weight loss outcomes. Therefore, the challenge is to develop interventions that facilitate the adoption and maintenance of these behaviors. We hypothesize that a mentor-based intervention will improve long-term weight loss in both mentors and mentor-recipients compared to individuals receiving a standard non-mentored-based weight loss intervention. We hypothesize that this improvement will be a result of increased contact with a structured program which result in the enhanced adoption and maintenance of healthful eating and exercise behaviors. Overweight Subjects will be recruited in two phases: 1) 58 subjects in Phase 1, and 2) 116 subjects in Phase 2. Subjects in Phase 1 that lose greater than or equal to 10 pounds within the initial 6 months of treatment will be randomized as a mentor or non-mentor for subjects in Phase 2. Subjects in Phase 2 will be randomize to receive or not receive a mentor (mentor-recipient versus non-mentor-recipient). Subject in Phase 1 will be followed for 24 months and subjects in Phase 2 followed for 18 months. Assessments will occur at 6 month intervals and will include body weight, body composition, fitness, eating and exercise behaviors, and mediators of behavior change. It is believed that a mentor- based intervention will lead to improvements in the long-term treatment of obesity.